Consumer Unit / Fuse Box

A consumer unit (informally called a fuse box or fuse board) is the main electrical panel in a UK home. It is where the incoming electricity supply from the mains is split into individual circuits — one for the kitchen sockets, one for the upstairs lights, one for the cooker, and so on. Each circuit is protected by a device (a circuit breaker or fuse) that automatically cuts the power if something goes wrong.

What is inside a consumer unit

• Main switch — the master on/off switch for the entire home’s electricity supply
• RCDs (Residual Current Devices) — safety switches that detect faults and cut power in milliseconds to prevent electric shock
• MCBs (Miniature Circuit Breakers) — individual switches protecting each circuit. They trip (switch off) if a circuit is overloaded or short-circuits
• RCBOs — combined RCD + MCB in a single device, giving each circuit its own independent fault protection

Why the consumer unit matters in a renovation

A consumer unit upgrade is one of the most common electrical requirements during a renovation:

• Adding circuits — a new kitchen, bathroom, or extension will need additional circuits (cooker, shower, sockets, lighting), which means more MCBs or RCBOs in the consumer unit
• Regulatory compliance — building regulations (Part P in England and Wales) require that any new electrical work meets current standards. If your existing consumer unit is old (particularly if it still has rewirable fuses or lacks RCD protection), it will likely need replacing
• Metal enclosure requirement — since 2016, UK regulations require consumer units to be housed in a non-combustible (metal) enclosure for fire safety
• First fix coordination — consumer unit work is part of the electrical first fix, done before walls are plastered and finished

Signs your consumer unit needs upgrading

• It contains rewirable fuses (ceramic holders with fuse wire) instead of modern MCBs
• It has no RCD protection
• It is in a wooden or plastic enclosure
• There are not enough ways (circuit slots) for your planned renovation
• It trips frequently under normal use

Practical tip

Consumer unit replacement must be done by a qualified electrician who is registered with a competent person scheme (such as NICEIC, NAPIT, or ELECSA in the UK). They will issue an Electrical Installation Certificate when the work is complete. Always ask for this certificate — you will need it when selling the property or for insurance purposes. Discuss the consumer unit early with your contractor so it is included in the scope of work.